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Abstract:

The present invention provides a heat-resistant adhesive sheet for
semiconductor device fabrication that is attached to a substrateless
semiconductor chip when the chip is encapsulated with resin. The adhesive
sheet includes a base material layer and an adhesive layer. The adhesive
layer contains a rubber component and an epoxy resin component. The
proportion of the rubber component in an organic substance in the
adhesive is in the range of 20 to 60 wt %.

Claims:

1. A heat-resistant adhesive sheet for semiconductor device fabrication,
the heat-resistant adhesive sheet being attached to a substrateless
semiconductor chip when the substrateless semiconductor chip is
encapsulated with resin, wherein: the adhesive sheet comprises a base
material layer and an adhesive layer, the adhesive layer contains a
rubber component and an epoxy resin component, and the proportion of the
rubber component in an organic substance in the adhesive is in the range
of 20 to 60 wt %.

2. The heat-resistant adhesive sheet for semiconductor device fabrication
according to claim 1, wherein the epoxy resin component has a weight per
epoxy equivalent of less than or equal to 1000 g/eq.

3. The heat-resistant adhesive sheet for semiconductor device fabrication
according to claim 1, wherein the adhesive layer contains a conductive
filler and is electrically conductive.

4. An adhesive for a heat-resistant adhesive sheet for semiconductor
device fabrication according to claim 1.

5. A semiconductor device fabrication method using a heat-resistant
adhesive sheet for semiconductor device fabrication according to claim 1
to resin-encapsulate a substrateless semiconductor chip that does not use
a metal lead frame.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a heat-resistant adhesive sheet
for semiconductor device fabrication used for fabrication of
substrateless semiconductor packages that do not use a metal lead frame,
an adhesive used for the sheet, and a method for fabricating a
semiconductor device using the sheet.

[0003] 2. Description of the Related Art

[0004] Among LSI packaging technologies, Chip Size/Scale Package (CSP)
technologies have recently come into attention. Among those technologies,
a package form that does not use a substrate and packs only chips, such
as Wafer Level Package (WLP), is especially attractive in terms of
packaging density and size reduction. In a WLP fabrication method,
multiple semiconductor Si wafer chips orderly arranged without the use of
a substrate are encapsulated with an encapsulation resin at a time and
then the wafer is diced into individual structures. Thus the method
enables packages smaller than conventional ones that use a substrate to
be fabricated efficiently.

[0005] In such a WLP fabrication method, chips, which are conventionally
fixed on a substrate, need to be fixed on an alternative supporter.
Furthermore, since the chips need to be unfixed after the chips have been
encapsulated with resin and formed into individual packages, the
supporter need to be removable, instead of permanent bonding fixation.
Therefore, an approach to using an adhesive tape as such a supporter for
temporarily fixing chips is known.

[0006] For example, Japanese Patent Laid-Open No. 2001-308116 describes a
chip electronic component fabrication method that includes the steps of:
attaching acrylic resin adhesion means onto a substrate, the adhesive
means being adhesive before processing but the adhesion strength
decreases after the processing; fixing a plurality of semiconductor chips
of the same type or different types onto the adhesion means with an
electrode-formed surface down; coating a whole area including interspaces
between the plurality of semiconductor chips of the same type or
different types with a protective material; applying predetermined
processing to reduce the adhesion strength of the adhesion means and
peeling off a pseudo wafer on which the semiconductor chips are fixed
from the semiconductor chips; and cutting the protective material between
the plurality of semiconductor chips of the same type or different types
to separate the semiconductor chips or chip electronic components.

[0007] Japanese Patent Laid-Open No. 2001-313350 describes a hip
electronic component fabrication method that includes the steps of:
attaching acrylic resin adhesion means onto a substrate, the adhesive
means being adhesive before processing but the adhesion strength
decreases after the processing; fixing a plurality of semiconductor chips
of the same type or different types onto the adhesion means with an
electrode-formed surface down; coating a whole area including interspaces
between the plurality of semiconductor chips of the same type or
different types with a protective material; removing the protective
material from the area from the side opposite of the electrode-formed
side to the side opposite of the semiconductor chips; applying
predetermined processing to reduce the adhesion strength of the adhesion
means and peeling off a pseudo wafer on which the semiconductor chips are
fixed from the semiconductor chips; and cutting the protective material
between the plurality of semiconductor chips of the same type or
different types to separate the semiconductor chips or chip electronic
components.

[0008] Indeed, according to these methods, the protection of the chips
also protects the chips during mounting/handling after dicing and the
packaging density can be improved.

[0009] Japanese Patent Laid-Open No. 2008-101183 describes a dicing/die
bonding tape including an adhesive layer containing epoxy resin and
acrylic rubber and a method for bonding a semiconductor device resulting
from dicing onto a supporter. Obviously, the method is not intended for
substrateless semiconductor devices and the adhesive layer is chosen by
taking into consideration the adhesiveness to a substrate.

[0010] The following problems can arise with the following method for
fabricating a substrateless semiconductor package using an adhesive tape
as a temporary supporter.

[0011] The problems will be described below with reference to FIG. 1,
which illustrates the substrateless semiconductor device fabrication
method.

[0012] A heat-resistant adhesive sheet 2 for semiconductor device
fabrication includes an adhesive layer 12 on one side and a substrate
fixing bond layer 13 on the other side. Multiple chips 1 are attached
onto the adhesive layer 12 of the heat-resistant adhesive sheet 2 for
semiconductor device fabrication and the sheet 2 is fixed on a substrate
3 with the substrate fixing bond layer 13 to form a structure illustrated
in part (a) of FIG. 1. Alternatively, the heat-resistant adhesive sheet 2
for semiconductor device fabrication is attached onto a substrate 3 and
chips 1 are fixed on the heat-resistant adhesive sheet 2 for
semiconductor device fabrication to form the structure depicted in part
(a) of FIG. 1.

[0013] Then, the chips 1 on the structure depicted in part (a) are
encapsulated together with an encapsulation resin 4 to form a structure
illustrated in part (b) of FIG. 1.

[0014] Then, as illustrated in part (c), the heat-resistant adhesive sheet
2, together with the substrate 3, is removed from the multiple chips 1
encapsulated with the encapsulation resin 4, or the multiple chips 1
encapsulated with the encapsulation resin 4 and the heat-resistant
adhesive sheet 2 are removed together from the substrate 3 and then the
heat-resistant adhesive sheet 2 for semiconductor device fabrication is
removed from the chips 1, thereby obtaining the multiple chips 1
encapsulated with the encapsulation resin 4.

[0015] Electrodes 5 are formed in desired positions on surfaces of the
chips 1 encapsulated with the encapsulation resin 4 that are exposed on
the side on which the heat-resistant adhesive sheet 2 for semiconductor
device fabrication is provided, thereby forming a structure depicted in
part (d).

[0016] For the step of dicing, a dicing tape 8 having a dicing ring 7
provided on its encapsulation resin 4 side as required is bonded to the
structure to fix the chips 1 encapsulated with the encapsulation resin 4.
The structure is diced with a dicing blade 6 as depicted in part (e) to
ultimately provide multiple substrateless packages in which multiple
chips are encapsulated with the resin as depicted in part (f).

[0017] During the resin encapsulation, the heat-resistant adhesive sheet 2
for semiconductor device fabrication illustrated in FIG. 2(a) can be
deformed in planar directions due to expansion and elasticity of a base
material layer or the adhesive layer of the heat-resistant adhesive sheet
2 for semiconductor device fabrication as illustrated in FIG. 2(b).
Accordingly, the positions of the chips 1 provided on the heat-resistant
adhesive sheet 2 for semiconductor device fabrication can move.

[0018] As a result, when the electrodes are provided on the chips 1,
relative positional relationship between the chips 1 and the electrodes
would have changed from the originally designed relationship.
Furthermore, during dicing of the chips 1 encapsulated with resin, the
dicing line based on the positions of the chips 1 predetermined for the
dicing step would be different from the dicing line required by the
actual positions of the chips 1.

[0019] Consequently, the positions of chips encapsulated in the packages
resulting from dicing would vary from one package to another and a
subsequent electrode formation step would not smoothly be performed and
partially encapsulated packages would result.

[0020] When the heat-resistant adhesive sheet 2 for semiconductor device
fabrication is peeled away from the resin-encapsulated chips, an adhesive
formed on the chip side of the heat-resistant adhesive sheet 2 for
semiconductor device fabrication exhibits heavy peeling from the chips or
the encapsulation resin, depending on the properties of the adhesive.
Therefore it can be difficult to peel off the heat-resistant adhesive
sheet 2 for semiconductor device fabrication, or adhesive deposits 9 as
illustrated in FIG. 3 can occur or static electricity can build up during
peeling.

[0021] As peeling becomes difficult, more time is required accordingly.
Heavy peeling therefore can lead to reduction in productivity. Adhesive
deposits 9 can inhibit a subsequent step such as electrode formation.
Static electricity build-up caused by peeling leads to a problem due to
adhesion of dust in a subsequent step.

[0022] As has been described, chips can be displaced from specified
positions by pressure applied during resin encapsulation because the
chips are not properly held in the substrateless semiconductor package
fabrication method using a heat-resistant adhesive sheet 2 for
semiconductor device fabrication as a supporter for temporary fixture.
When the heat-resistant adhesive sheet 2 for semiconductor device
fabrication is peeled off, packages can be damaged by adhesion strength
to the chips increased by curing of the encapsulation material or heat.

[0023] Furthermore, if gas is generated from the adhesive layer or part of
the adhesive is eluted from the adhesive layer under heat generated
during use of the device, the gas or adhesive can contaminate the
surfaces of the chips and subsequent steps such as the electrode
formation step cannot reliably be performed, thus resulting in poor
connections.

[0024] These problems are specific to substrateless semiconductor device
fabrication methods not suffered by other methods such as the method
described in Japanese Patent Laid-Open No. 2008-101183.

SUMMARY OF THE INVENTION

[0025] Means for solving the problems is as follows.

[0026] A heat-resistant adhesive sheet for semiconductor device
fabrication is attached to a substrateless semiconductor chip when the
substrateless semiconductor chip is encapsulated with resin. The
heat-resistant adhesive sheet includes a base material layer and an
adhesive layer. The adhesive layer contains a rubber component and an
epoxy resin component. The proportion of the rubber component in an
organic substance in the adhesive is in the range of 20 to 60 wt %.

[0027] Alternatively, the epoxy resin component may have a weight per
epoxy equivalent of less than or equal to 1000 g/eq, the adhesive layer
may contain a conductive filler to impart electrical conductivity and
high elasticity to the adhesive layer.

[0028] Furthermore, there is provided a semiconductor device fabrication
method that resin-encapsulates a substrateless semiconductor chip using
the heat-resistant adhesive sheet 2 for semiconductor device fabrication,
instead of a metal lead frame.

[0029] The present invention provides an adhesive sheet for temporarily
fixing chips, used in a method for fabricating a substrateless
semiconductor package that does not use a metal lead frame (for example a
method for fabricating WLP), an adhesive used in the adhesive sheet, and
a method for fabricating a semiconductor device using the adhesive sheet.
The adhesive of the present invention contains an appropriate content of
a rubber component to add flexibility to the adhesive sheet without
impairing heat resistance of the adhesive sheet. Accordingly, the
adhesive sheet exhibits good machinability in cutting of the adhesive
sheet.

[0030] Therefore, the adhesive sheet holds the chips so that the chips are
not displaced from specified positions during resin encapsulation and
does not leave adhesive deposits after the adhesive sheet has been used.
Furthermore, contamination with outgas and eluted substances does not
occur and an adhesive does not melt and attach during heating.
Consequently, defects are not caused in forming electrodes and
interconnects on chip surfaces.

[0031] The present invention can improve the fabrication yield of the
semiconductor packages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a schematic diagram of a method for fabricating a
substrateless package;

[0033] FIG. 2 is a diagram illustrating deformation of a heat-resistant
adhesive sheet for semiconductor device fabrication on which chips are
mounted by heat during encapsulation with encapsulation resin;

[0034] FIG. 3 is a diagram illustrating static electricity build-up and
adhesive deposits that occur when a heat-resistant adhesive sheet for
semiconductor device fabrication is removed; and

[0035] FIG. 4 is a cross-sectional view of a heat-resistant adhesive sheet
for semiconductor device fabrication according to the present invention.

[0049] The present inventor has diligently worked on adhesive sheets and
has found that the use of a certain rubber-epoxy-based adhesive in the
adhesive layer of a heat-resistant adhesive sheet for semiconductor
device fabrication allows the adhesive sheet to exhibit high heat
resistance after curing, appropriate adhesion to semiconductor packages
during resin encapsulation, and good peelability after the resin
encapsulation without leaving adhesive deposits, as described in
description of means for solving the problems. The present inventor has
thus made the present invention.

[0050] The present invention provides a heat-resistant adhesive sheet for
semiconductor device fabrication that is attached to substrateless
semiconductor chips that do not use a metal lead frame when the chips are
encapsulated with resin. The heat-resistant adhesive sheet includes a
base material layer and an adhesive layer. The adhesive layer contains a
rubber component and an epoxy resin component. The proportion of the
rubber component in an organic substance in the adhesive is in the range
of 20 to 60 wt %.

[0051] According to the present invention, since the adhesive sheet does
not contain a silicone component, the adhesive sheet does not cause
contamination which would otherwise be caused by outgas and eluted
substances, keeps sufficient elasticity at high temperatures, and hardy
leaves adhesive deposits. Furthermore, the appropriate content of rubber
component contained in the adhesive adds flexibility to the adhesive
without impairing the heat resistance, thereby improving the
machinability during cutting of the heat-resistant adhesive sheet for
semiconductor device fabrication.

[0052] The epoxy resin component of the adhesive layer preferably has a
weight per epoxy equivalent of less than or equal to 1000 g/eq. A weight
per epoxy equivalent of 1000 g/eq or less makes the crosslink density
moderate and therefore can more reliably inhibit adhesive deposits during
peeling.

[0053] A heat-resistant adhesive sheet for semiconductor device
fabrication, an adhesive used in an adhesive layer of the heat-resistant
adhesive sheet for semiconductor device fabrication, and a method for
fabricating a semiconductor device using the heat-resistant adhesive
sheet according to the present invention will be described below in
detail with reference to drawings.

[0054] FIG. 4 is a cross-sectional view of a heat-resistant adhesive sheet
2 for semiconductor device fabrication. The heat-resistant adhesive sheet
2 for semiconductor device fabrication includes a base material layer 11
and an adhesive layer 12. A substrate fixing bond layer 13 may be formed
on the surface of the base material layer on which the adhesive layer is
not provided, so that the heat-resistant adhesive sheet 2 for
semiconductor device fabrication having chips 1 fixed on the adhesive
layer 12 can be fixed onto a substrate 3. The adhesive layer 12 is a
layer of an adhesive containing a rubber component and an epoxy resin
component.

[0055] Flat, smooth peeling sheets 10 that protect the surfaces of the
adhesive layer 12 and the substrate fixing bond layer 13 may also be
provided.

[Adhesive Layer 12]

(Rubber Component)

[0056] Examples of the rubber component used include NBR
(acrylonitrile-butadiene rubber), acrylic rubber, acid terminated nitrile
rubber, and thermoplastic elastomer. Examples of commercially available
rubber components include NiPol 1072 (from Zeon Corporation) and
Nipol-AR51 (from Zeon Corporation). Among them, NBR is preferably used in
terms of compatibility with epoxy resin. In particular, NBR having an
acrylic nitrile content of 10 to 50% is preferable.

[0057] The aim of addition of the rubber component is to impart
flexibility to the adhesive. However, the heat resistance decreases as
the content of the rubber component increases. In view of this, the
proportion of the rubber component in an organic substance in the
adhesive layer is preferably in the range of 20 to 60 wt %, more
preferably 20 to 50 wt %. A proportion in the range of 20 wt % to 60 wt %
can suppress reduction in flexibility of the adhesive layer and maintain
the machinability in cutting of the heat-resistant adhesive sheet for
semiconductor device fabrication. In addition, such a content can
suppress reduction in heat resistance and suppress adhesive deposits.

[0059] The proportion of the epoxy resin component is preferably in the
range of 40 to 80 wt %, more preferably 50 to 70 wt %, for 100 wt % of an
organic substance. 40 wt % to 80 wt % of epoxy resin allows the adhesive
to cure sufficiently and to have high heat resistance. The proportion of
the epoxy resin also can suppress reduction of the flexibility and
maintain high machinability. The epoxy resin has a weight per epoxy
equivalent of less than or equal to 1000 g/eq, preferably less than or
equal to 700 g/eq, yet preferably less than or equal to 300 g/eq. A
weight per epoxy equivalent of 1000 g/eq or less can suppress reduction
in crosslink density, prevent increase of bonding strength after curing,
and suppress adhesive deposits during peeling after encapsulation.

(Composition of Adhesive)

[0060] A conductive filler can be blended in the adhesive layer 12 of the
present invention. The conductive filler adds an antistatic property to
the adhesive layer 12 and therefore prevents buildup of static charge in
the heat-resistant adhesive sheet 2 for semiconductor device fabrication
and chips during peeling of the adhesive sheet 2 from the chips after
use.

[0061] The heat-resistant adhesive sheet for semiconductor device
fabrication of the present invention fixes chips before the chips are
encapsulated with resin and can be smoothly peeled away from the chips
and the resin used for the encapsulation after the encapsulation with
resin. The resin encapsulation is performed at approximately 175°
C. The heat-resistant adhesive sheet for semiconductor device fabrication
of the present invention needs to be able to be used with stable quality
and not excessively stretch at such high temperature. The adhesive layer
should not soften at such high temperature.

[0062] Preferably, a curing agent that cures epoxy resin, which is a
curable component, is added to the adhesive layer 12 of the present
invention. Examples of the epoxy resin curing agent that can be used
include phenol resin, imidazole-based compounds and their derivatives,
hydrazide compounds, dicyandiamide, and microencapsulates of these. In
particular, if phenol resin is used as the curing agent, a phosphorous
compound such as triphenyl phosphine can be used as a curing accelerator.

[0063] If phenol resin is chosen as the curing agent, a portion of the
additive amount of epoxy resin can be replaced with phenol resin so that
the equivalent weight of the curing agent is approximately equal to the
equivalent weight of epoxy resin.

[0064] The proportion of other curing agent and the curing accelerator is
in the range of 0.5 to 5 wt %, preferably 0.5 to 3 wt %, for 100 wt % of
organic substance.

[0065] Known additives such as an inorganic filler, an organic filler,
pigment, an anti-aging agent, a silane coupling agent, and a tackifier
can be added to the adhesive layer as required, as long as the properties
of the heat-resistant adhesive sheet for semiconductor device fabrication
are not degraded. In particular, addition of the anti-aging agent is
effective for inhibiting deterioration at high temperature.

[Base Material Layer 11]

[0066] A material for the base material layer 11 is not limited to a
particular type. Any base material that is heat-resistant under heating
conditions during resin encapsulation can be used. Since the resin
encapsulation step is performed typically at a temperature around
175° C., a base material used is preferably heat-resistant so that
the base material does not significantly contract or the base material
layer 11 itself is not damaged at such temperatures. Accordingly, the
base material has preferably a linear thermal expansion coefficient of
0.8×10-5 to 5.6×10-5/K at a temperature of 50 to
250° C.

[0067] If a base material that has a glass transition temperature lower
than the heating temperature for curing the encapsulation resin 4 is used
as the base material, the linear thermal expansion coefficient of the
base material in a range of temperatures higher than the glass transition
temperature will be higher than the linear thermal expansion coefficient
in a range of temperatures lower than the glass transition temperature.
Accordingly, displacement of adhered chips 1 from specified positions
will increase.

[0068] In addition, a uniaxially- or biaxially-stretched base material,
which was stretched at a temperature higher than its glass transition
temperature, starts contracting at a temperature lower than the glass
transition temperature, which also increases displacement from the
specified positions of the adhered chips. The positional accuracy of the
chips can be improved by choosing a material that has a glass transition
temperature higher than 180° C. as the material of the base
material layer 11 of the heat-resistant adhesive sheet 2 which is
attached to the substrateless semiconductor chips without a metal lead
frame when the chips are encapsulated with resin can.

[0070] If the temperature at which the resin encapsulation is performed is
less than or equal to 150° C., a polyethylene terephthalate (PET)
film can be used.

[0071] The heat-resistant base material layer 11 may be made of a paper
base material such as glassine paper, quality paper, or Japanese paper,
or nonwoven fabric base material of cellulose, polyamide, polyester,
aramid, or the like, or a metal film base material such as aluminum foil,
SUS foil, or Ni foil. These materials may be stacked to form the base
material layer 11.

[0072] The thickness of the base material layer 11 is 10 to 200 μm,
preferably 25 to 100 μm, in order to prevent a rip and break. A
thickness of 10 μm to 200 μm provides a good handling ability.

[Substrate Fixing Bond Layer 13]

[0073] A bond used for the substrate fixing bond layer 13 may be a
material that has such bonding strength that the substrate fixing bond
layer 13 can be peeled away from the substrate 3 or the base material
layer 11, or may be the same adhesive as that of the adhesive layer 12.

[0074] Peeling of the heat-resistant adhesive sheet 2 away from the
substrate 3 can be facilitated by heating if for example a blowing agent
that is foamed by heat is added to the substrate fixing bond layer 13.
Instead of means that changes by heat, a component that forms cross-links
under UV irradiation, for example, can be added to the substrate fixing
bond layer 13 beforehand so that the substrate fixing bond layer 13 is
cured, thereby reducing adhesion strength of the substrate fixing bond
layer 13.

[0075] By such treatment, the adhesion strength of the substrate fixing
bond layer 13 is reduced to separate the substrate 3 and the substrate
fixing bond layer 13 from each other, or to separate the base material
layer 11 and the substrate fixing bond layer 13 from each other, thereby
removing the chips encapsulated with resin from the substrate 3.

[Flat, Smooth Peeling Sheet 10]

[0076] The flat, smooth peeling sheet 10 is formed of a base material film
having a peeling agent layer formed on one side of the base material film
and is peeled to expose the adhesive layers on both sides before the
heat-resistant adhesive sheet 2 for semiconductor device fabrication is
used.

[0077] The peeling agent layer contains a known peeling agent, such as a
known fluorinated silicone resin-based peeling agent, a fluororesin
peeling agent, a silicone resin-based peeling agent, polyvinyl
alcohol-based resin, polypropylene-based resin, or long-chain alkyl
compound, chosen according to the type of resin of the adhesive layer.

[0079] According to the present invention, compositions prepared as
described above can be used to form a heat-resistant adhesive sheet for
semiconductor device fabrication by any of method generally used for
fabricating a multilayer structure. In one method, the composition is
dissolved in a solvent, then is applied to a base material film, and
dried by heating to form a heat-resistant adhesive sheet for
semiconductor device fabrication. In another method, the composition is
dissolved in a solvent to make an aquatic dispersion solution, and the
solution is applied to a base material film and dried by heating to form
a heat-resistant adhesive sheet for semiconductor device fabrication.

[0080] The solvent is preferably, but is not limited to, a ketone-based
solvent, such as methyl ethyl ketone, which provide a good solubility.

[0081] The heat-resistant adhesive sheet 2 for semiconductor device
fabrication of the present invention includes the adhesive layer thus
formed to a typical thickness of 1 to 50 μn on the base material layer
and is used in the form of a sheet or tape, or other form.

[0082] The heat-resistant adhesive sheet 2 for semiconductor device
fabrication can be provided with an antistatic function as required. A
method for providing an antistatic function to the heat-resistant
adhesive sheet 2 for semiconductor device fabrication is to add an
antistatic agent or conductive filler to the adhesive layer 12 and the
base material layer 11. Another method is to provide an antistatic agent
layer at the interface between the base material layer 11 and the
adhesive layer 12 or between the base material layer 11 and the substrate
fixing bond layer 13. The antistatic function can suppress buildup of
static electricity caused while the heat-resistant adhesive sheet 2 for
semiconductor device fabrication is being peeled off from the
semiconductor device.

[0083] The antistatic agent may be any agent that has the antistatic
capability. Examples of the antistatic agent include surfactants such as
acrylic-based ampholytic, acrylic-based cation, and maleic
anhydride-styrene-based anion.

[0084] Examples of the material for the antistatic layer include Bondeip
PA, Bondeip PX, and Bondeip P (from Konishi Co., Ltd.). The conductive
filler may be a conventional one, for example a metal such as Ni, Fe, Cr,
Co, Al, Sb, Mo, Cu, Ag, Pt, or Au, or an alloy or oxide of any of these,
or a carbon such as carbon black. These materials can be used either
singly or in combination.

[0085] The conductive filler may be powdery or fibrous filler.

[0086] The heat-resistant adhesive sheet 2 for semiconductor device
fabrication thus fabricated has an excellent heat resistance and a good
demoldability from packages and therefore is suited for use in a
semiconductor device manufacturing process.

WORKING EXAMPLES

[0087] A measuring method used in working examples is as follows.

[0088] Initial adhesion strength to SUS: Peel adhesion strength to a
SUS304BA plate at an angle of 180° at room temperature

[0089] Peel strength from package: Peel adhesion strength at an angle of
180° when the adhesive tape is peeled from the package

[0090] Chip displacement: Displacement from the initial position of a chip
measured with a digital microscope after package fabrication

[0091] Adhesive deposit: The surface of the package was visually checked
for adhesive deposits after the adhesive tape was peeled off.

[0092] The present invention will be descried more specifically with
respect to working examples. The term "part" in the following description
means "part by weight".

Working Example 1

[0093] 42 parts of acrylonitrile-butadiene rubber (Nipol 1072) from Zeon
Corporation), 53 parts of bisphenol A-type epoxy resin (Epikote 828 from
Japan Epoxy Resin Co., Ltd., with a weight per epoxy equivalent of 190
g/eq), and 5 parts of imidazole (C1 1Z from Shikoku Chemicals
Corporation) were blended and dissolved in an MEK solvent to a
concentration of 35 wt % to prepare a bond solution. The bond solution
was applied to a 35-μm-thick copper foil serving as a base material
film, and was then dried at 150° C. for 3 minutes to form an
adhesive layer having a thickness of 10 μm, thus forming a
heat-resistant adhesive sheet for semiconductor device fabrication.

[0094] A 3 mm×3 mm Si wafer chip was placed on the heat-resistant
adhesive tape, epoxy-based encapsulation resin powder (GE-740LA from
Nitto Denko Corporation) was sprinkled over the tape and the wafer chip,
and then molded by heating at a temperature of 175° C. under a
pressure of 3.0 kg/cm2 for 2 minutes. Then the structure was heated
at 150° C. for 60 minutes to accelerate curing of the resin
(post-mold cure) to complete a package.

Working Example 2

[0095] 24 parts of acrylonitrile-butadiene rubber (Nipol 1072) from Zeon
Corporation), 65 parts of bisphenol A-type epoxy resin (Epikote 1002 from
Japan Epoxy Resin Co., Ltd., with a weight per epoxy equivalent of 650
g/eq), 10 parts of phenol resin (P-180 from Arakawa Chemical Industries,
Ltd.), and 1 part of triphenylphosphane (TPP from Hokko Chemical
Industry) were blended and dissolved in an MEK solvent to a concentration
of 35 wt % to prepare an adhesive solution. The adhesive solution was
applied to a 35-μm-thick copper foil serving as the base material
film, and was then dried at 150° C. for 3 minutes to form an
adhesive layer having an adhesive thickness of 10 μm, thus forming a
heat-resistant adhesive sheet for semiconductor device fabrication. The
rest of the method for fabricating the package was the same as that in
Working Example 1.

Comparative Example 1

[0096] 70 parts of acrylonitrile-butadiene rubber (Nipol 1072) from Zeon
Corporation), 28 parts of bisphenol A-type epoxy resin (Epikote 828 from
Japan Epoxy Resin Co., Ltd., with a weight per epoxy equivalent of 190
g/eq), and 2 parts of imidazole (C1 1Z from Shikoku Chemicals
Corporation) were blended and were dissolved in an MEK solvent to a
concentration of 35 wt % to prepare an adhesive solution. The adhesive
solution was applied to a 35-μm-thick copper foil serving as a base
material film and was then dried at 150° C. for 3 minutes to form
an adhesive layer having an adhesive thickness of 10 μm, thus forming
a heat-resistant adhesive sheet for semiconductor device fabrication. The
rest of the method for fabricating the package was the same as that in
Working Example 1.

Comparative Example 2

[0097] 10 parts of acrylonitrile-butadiene rubber (Nipol 1072) from Zeon
Corporation), 79 parts of bisphenol A-type epoxy resin (Epikote 1002 from
Japan Epoxy Resin Co., Ltd., with a weight per epoxy equivalent of 650
g/eq), 10 parts of phenol resin (P-180 from Arakawa Chemical Industries,
Ltd.), and 1 part of triphenylphosphane (TPP from Hokko Chemical
Industry) were blended and dissolved in an MEK solvent to a concentration
of 35 wt % to prepare an adhesive solution. The adhesive solution was
applied to a 35-μm-thick copper foil serving as the base material
film, and was then dried at 150° C. for 3 minutes to form an
adhesive layer having an adhesive thickness of 10 μm, thus forming a
heat-resistant adhesive sheet for semiconductor device fabrication. The
rest of the method for fabricating a package was the same as that in
Working Example 1.

[0098] In the adhesive tapes and packages fabricated as described above,
the peel adhesion strength to an SUS304BA plate at an angle of
180° at room temperature (hereinafter referred to as the initial
adhesion strength), the peel adhesion strength when the adhesive tape is
actually peeled off from a package (hereinafter referred to as peel
strength), the displacement of the chip from its initial position, and
adhesive deposits left after the adhesion tape was peeled were as given
below.

[0099] As apparent from Table 1, the adhesive sheets of Working Examples 1
and 2 of the present invention exhibited an excellent demoldability for
packages and did not left adhesive deposits. Furthermore, since the
adhesive sheets had sufficient initial adhesion strength and the adhesive
layers were not too soft, chip displacement by encapsulation resin was
suppressed.

[0100] In contrast, the adhesive sheet of Comparative Example 1 with a
large amount of rubber component unlike the ones of the present invention
had sufficient initial adhesion strength but caused chip displacement
during resin encapsulation because the adhesive layer was soft. In
addition, the adhesive sheet had poor elasticity after cured and left
adhesive deposits. The adhesive sheet of Comparative Example 2 with a
small amount of rubber component had insufficient initial adhesion
strength and therefore caused chip displacement during resin
encapsulation.